text:
Is there an aerodynamic benefit of covering the underside of wings?
What is the nature and extent to the benefit of covering up the bottom of an airfoil?
It seems like all the early airplanes just had ribs and spars that were wrapped only on top, but then pretty soon wings started getting wrapped underneath too.
Despite the added weight of covered wing bottoms, I'm assuming that the planes flew much better this way.
Are there any resources about experiments on covered vs exposed wing bottoms? How much less aerodynamic is it to leave them exposed?

Lift is a function of velocity squared.  As more powerful engines became available, higher airspeeds allowed designers to choose the airfoil shape that provided the least amount of drag for a given amount of lift at that airspeed.
Undercambered wings, as seen on the Bleriot XI which flew at around 40 knots were replaced by "filled in" or covered wing bottoms, as seen on the Fokker D7, which flew at around 100 knots.
A little undercamber is still there, and is also seen on the famous Clark Y airfoil.
As things got faster, up to 200 knots, the bottom was filled in completely, becoming convex, as seen on the Davis airfoil.
These wings served well until even faster speeds demanded consideration of Mach factors, especially in areas over the wing where airflow is accelerated, which lead to these "supercritical" wings, in use today on jet airliners.

There most certainly is, early hang gliders we’re single-surface, then more advanced designs adopted a small under-surface just behind the leading edge, and the extend of the lower surface increased with higher-performing designs.  That’s not exactly experimental per se but a reflection of the development work done as that aircraft type evolved.


text:
Confused about flight distance and flight time
I'm having a hard time understanding how the flight times of these flight are so different.
I looked up PDX (Portland, Or) to DEN (Denver, Co) is roughly 923 miles, with a flight time of 2h30m to DEN and 2h45m to PDX.
BUR (Burbank, Can) to PDX is 831 miles with a flight time of 3h30m.
How is a longer distance flight take less time?
All Southwest, they only have 737-700, 737-800, and 737-800 MAX.  Referring too only non-stop flights.

What planes were being used? How many stops did the flights have?

Alaska Airlines 317 from BUR to PDX takes typically a little over 2 hours on a B737 according to FlightAware.

Where did you get these times from? Are they just the airborne time or are they gate-to-gate? Are they the same airline, the same aircraft type?

Departure delays getting out of a small, non-primary airport in SoCal can be significant.

Don't you see "1 stop - no plane change" on BUR to PDX?

Using SimBrief, I filed two example flight plans: One from PDX to DEN and one from BUR to PDX. As you can see in the images below, the former route has a continuous light tailwind, while the latter route has a moderate crosswind. Despite this, using an A320 as our reference, BUR to PDX takes 17 minutes less than PDX to DEN. Please verify where you got your information from.
PDX to DEN. Note the "dashes" that indicate wind direction and velocity.

BUR to PDX.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Is my procedure correct for simulated flight approach using this IAP after complete STAR?
I usually "fly" with flightsimulator (FlightGear, because is O.S. and freeware).
I try to make the fly real as possible, and I try to use IAP, is this procedure correct to
approach RWY 28 of LSZH Zurich Airport?

I'm on FIX AMIKI, I can use this IAP after complete STAR
AMIKI then KLO then 84° and at D16(16 miles distance from KLO) i take 275° and allign to ILS?
Or I make all/something wrong?
How did you proceed to enter in RWY 28 ils?
Thanks

I fixed the question with correct terms, thanks

I think the procedure envisions a teardrop entry into the holding pattern at KLO to reverse your course and get back to KLO in a position that you can commence the procedure track to the east.
So, the steps would be:

AMIKI
ZUE
KLO
outbound on a 234 track for 1 minute (the teardrop entry)
Right turn & inbound to KLO on the 084 inbound course
Outbound to the KLO 084/16
Right turn & intercept the ILS

And this is why ATC is your friend with Vectors.  (two course reversals?!)

@MichaelHall I didn't claim I thought it'd be fun!  Yes, definitely, vectors to final, thank you.

I agree with @Bianfable's answer, which explains the other options & why these steps would be required. My answer elaborates on his 3rd point. His early observation that radar vectors is what you'd expect in reality, is spot-on.

Thanks, why one minute? I cannot find in my chart

@elbarna The one minute is just the standard way of flying the teardrop entry into a holding pattern. You won't find it on the chart. Technically, you could fly any entry into the hold as long as you stay in the protected area, but a teardrop entry with a one minute leg is the recommended procedure in this case.

Thanks, now is clear

First of all, what you show is not a STAR. There are several STARs at LSZH that end at AMIKI (NEGRA 2A, RILAX 2A, TRA 2A). What happens after AMIKI is the approach transition.
There are 3 ways to get from AMIKI to the ILS for runway 28:

Radar Vectors: ATC will give you vectors onto final approach. This would most likely happen in reality

RNAV Transition: There is an RNAV transition from AMIKI to RAMEM called AMIKI28 transition:

AMIKI - ZH382 - ZH450 - ZH452 - ZH454 - ZH456 - ZH458 - ZH460 - ZH464 - RAMEM

If your aircraft is RNAV 1 capable (GNSS or DME/DME required), this would be the preferred transition to fly. From RAMEM (the D10.3 point on your chart), you can start the ILS approach.

Radio-based Transition: This is what you show on your ILS chart. You would only fly this if you don't get radar vectors and are not RNAV 1 certified.

Regarding your description of the procedure: you have a problem when arriving from ZUE at KLO. You cannot directly turn outbound to 084° because the change in course is too much. ICAO PANS-OPS only allows up to 30° turns when aligning for the reversal procedure:

Unless the procedure specifies particular entry restrictions, reversal procedures shall be entered from a track within ±30° of the outbound track of the reversal procedure. However, for base turns, where the ±30° direct entry sector does not include the reciprocal of the inbound track, the entry sector is expanded to include it.

(ICAO Document 8168, Vol 1 §4, 3.3.3.1)
Therefore, what you'd have to do is enter the hold at KLO and use the hold to align yourself with the outbound track of 084°. Then you continue the procedure as described.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What aircraft was I flying in?
In 1989 I was taking my first flying lesson. We were in a plane that had a low wing single engine and 2 seats if I recall correctly. After taking off on my first lesson the instructor was talking about radio and navigation settings and when retrieving a manual hit the door latch with his elbow and the door flew up and bent the tub connect to the frame of the plane. The hinges ripped out of the frame and was severely bent preventing it from being closed for about 6 ".He held the door while I flew the plane under his careful instruction ..I had flown hundreds of hours on a computer flight simulator on my home PC. Nevertheless he held the door while I navigated back to our original take off location in Lincoln park, nj...when back in the area he resumed control of plan while I reached across him to hold the door. He dropped the plane down and we landed safely.  Can anyone name the aircraft manufacturer and model...I want to write a story about my first flying lesson and need to know that info ..thx Frank

How it could be the instructor did not tell the model of the aircraft?

Perhaps you could give more hints? There are very many low wing single engine 2-seat aircrafts, many of whom had accidents at one point or another. Perhaps color, where you flew from or any other information (registration perhaps?) would help. However with the currently given information, I fear that the question cannot be answered...

What does your log book call it?  (could be a Piper Tomahawk or Beechcraft Skipper)

Was it fabric covered or metal?

Somehow I get the feeling this never happened, except maybe in that simulator...

@JuanJimenez Hundreds of simulator hours on a home PC in 1989? Everything about this question seems a bit of a fantasy "memory". Those were the days of 1.2MB floppy disks and Oregon Trail on a green monochrome. RAM was well above $200 per MiB(Not adjusted to 2022 dollars)

@MaxPower MS Flight Simulator 1.0 was released in 1982 for the IBM PC. It was in version 3.0 in 1988. I probably had hundreds of hours on it by 1989. I also got my PPSEL in Jan 89 after 6 months training in Beech Skipper. From his description, I would think it was not a Skipper. The lower rear door latches were very unreliable, but there was a single overhead latch that grabbed both doors very securely. Realistically though, if the latches get popped when flying, the door just opens an inch or so and makes lots of noise. It's on the ground that the door can be damaged by a gust of wind.


text:
Difference between the lift coefficient of the wing-profile and the wing
Let $ c_l $ the wing-profile lift coefficient and $ c_L $ the wing lift coefficient. For small values for the angle of attack $ \alpha $ both coefficients are linearly approximated:
$$ c_l(\alpha)=C_{l_{\alpha}}\cdot (\alpha-\alpha_0)\\[10pt] c_L(\alpha)=C_{L_{\alpha}}\cdot (\alpha-\alpha_0) $$
$ C_{l_{\alpha}} $ is the change of lift coefficient of the wing-profile and $ C_{L_{\alpha}} $ is the change of lift coefficient of the wing and $ \alpha_0 $ describes the angle where the lift is equal to zero. Both values $ C_{l_{\alpha}} $ and $ C_{L_{\alpha}} $ are given in the unit $ \frac{1}{\text{rad}} $. I also know the following relation between these two values given by:
$$ C_{L_{\alpha}}=\frac{C_{l_{\alpha}}}{1+\frac{C_{l_{\alpha}}}{\pi \cdot \Lambda\cdot \tau}} \quad (*)$$ and $ \Lambda $ is the stretch of the wing and $ \tau $ is the wing outline factor.
From here I'm getting confused about the unit's if I look at the formular $(*)$. The value $ C_{l_{\alpha}} $ is given in $ \frac{1}{\text{rad}} $. But in $(*)$ I'm adding the number $1$ with something with the unit $ \frac{1}{\text{rad}} $ which doesn't make sense to me. What went wrong here in the formular $(*)$?

By a practical point of view rad can be seen as a dummy unit of measurement, used to signal that angles are not measured in degrees.
For example, a circle's circumference is $2\pi r$ and if $r$ is in meters then the circumference is in meters as well and not in rad$\cdot$m. If a platform is rotating at 10rad/s and something stands on the platform at 2 meters from the center, its speed is 10$\cdot$2=20m/s and not 20rad$\cdot$m/s.
As a general rule, stay consistent with units of measurement.
Btw: 1) where did you get that equation? 2) what's $ \Lambda $ the stretch of the wing? 3) And what's $ \tau $ is the wing outline factor?

Ok. But if I have $ C_{l_\alpha} $ given in $ \frac{1}{\text{rad}} $ is the value $ C_{L_\alpha} $ also already in $ \frac{1}{\text{rad}} $ or should I scale $ C_{l_\alpha} $ scale back to $ \frac{1}{\text{deg}} $ and turn the result $ C_{L_\alpha} $ into $ \frac{1}{\text{rad}} $?

Everything must be consistent, if the author of that equation says to use 1/rad then 1/rad has to be used. Anyway $C_{l_\alpha}$ should be some 2π with good approximation. Btw where did you get that equation from?

But which way do I have to choose now? I'm confused. I got that equation from my lesson.

I don't understand now what's the matter... In the equation $C_{l_\alpha}$ has to be in 1/rad i.e. the angles not in degrees. What's the "stretch of the wing"?

"In the equation Clα has to be in 1/rad i.e". But is the result also in 1/rad? $ \Lambda=\frac{b^2}{S} $ and b is the wingspan and S the surface of the projected wing area.

The results is in 1/rad as well unless otherwise noted. Ah ok, the aspect ratio, never heard of stretch of the wing.

Re "Rad is not a real unit of measurement," -- sure it is-- approx  equal to 57.3 degrees.  There's a valid counter-argument to the logic of your second paragraph, but this isn't math s.e., so I won't go to deeply into that --

@quietflyer: yes I know, anyway thanks for saving us the related math :D

But math is beautiful. :D ;)

That's true ;) Anyway wait at least 24 hours before accepting an answer to give all people around the world the possibility to give an answer

@sophit: I don't understand what are you meaning by that.


text:
How can I get a report from the FAA stating that I haven't had any accidents?
To validate my FAA licence in Argentina and fly aircraft with LV tail numbers they require some documents, one of which is a report that states that I haven't been in any accidents. This report must come from the agency that issued my rating, in my case the FAA. I have not found any information on how to request this report from the FAA.

The FAA offers a dedicated website for requesting enforcement records at https://aie-pa.faa.gov/.
Additional guidance from the FAA is available here:

If you require a verification letter of your FAA airman certificate, for a Foreign Civil Aviation Authority, the request must come directly from the Foreign Civil Aviation Authority to the FAA. We will reply only to the official email address for the Foreign Civil Aviation Authority.
To check the validity of certificates for accident, incident and enforcement information visit https://aie-pa.faa.gov/ to submit your request.

The note about requests only being accepted directly from the foreign authority only applies to certificate verification.
I tried this out, and within an hour I got back an official-looking PDF with the FAA seal and a signature:

Control Number: 2023-xx-xxxxxxx-P
This is in response to your July 26, 2023 request seeking records through FAA’s Accident, Incident and Enforcement (AIE) portal. Specifically, you requested the following pertaining to (MY NAME): 1) basic EIS enforcement action information pertaining to closed investigations only; 2) summary data on any accidents or incidents in the airman’s record (within the AIDS system); 3) CAIS records (Certificate verification).
A search of the Accident/Incident Data System and Enforcement Information System on July 26, 2023, revealed no Accident/Incident or Enforcement record(s) concerning the above individual.

(Phew, glad there was nothing there I didn't know about!)


text:
Why does ATC in the US say "heavy" after callsigns but usually not in Europe?
In the United States, you'll often hear the word "heavy" after call signs used for wide-body planes over the radio during air traffic control (ATC) communications. However, in Europe, this practice isn't as common and you won't typically hear "heavy" being used by ATC. Why is that?

Europe complies with ICAO Doc 4444, §4.9.2: Heavy is used on initial contact. Doc 4444 is not mandatory (see this question). US difference from §4.9.2 is indicated in US AIP at section GEN 1.7: Heavy used in all contacts.

According to the Standardised European Rules of the Air (SERA), section 14 Voice Communication Procedures, SERA.14090 Special communication procedures, paragraph (c):

Indication of heavy wake turbulence category

For aircraft in the heavy wake turbulence category, the word ‘Heavy’ shall be included immediately after the aircraft call sign in the initial radiotelephony contact between such aircraft and ATS units.
For specific aircraft in the heavy wake turbulence category, as identified by the competent authority, the word ‘Super’ shall be included immediately after the aircraft call sign in the initial radiotelephony contact between such aircraft and ATS units.

So, an aircraft in the heavy or super wake turbulence category shall include the word Heavy or Super after the call sign in the initial contact with ATS.
If you don't hear this, then there are a couple of possibilities:

What you are hearing is not the initial contact.
What you are hearing is communication between the aircraft and something other than ATS.
The aircraft is not, in fact, in the heavy category. (Note that there is some slight difference in classification between, e.g., the FAA in the US, the CAA in the UK, the EASA in Europe, or the ICAO.)
The pilots made a mistake. They are human, after all.


text:
Can the cockpit windows on commercial airliners open during flight?
I  observed that the cockpit windows on the commercial airliners actually open - good for a hot day while waiting on the airfield, I suppose. Is there a mechanism which prevents the window from being opened when airborne?

I'm sure that the cabin pressure difference prevents this at altitude when the cabin is pressurized, due that they often slide inwards and then to the side.
That being said, Boeing produced a video showing that it's no problem flying with an open window on the 737 if say it opens on takeoff. You can close it assuming it's not damaged or you can land with it. They also showed that the side window can be opened in flight in case for instance visibility is impaired through the main window, and while it hardly looks comfortable, it can be done. This assumes that the cabin is unpressurized.
The sort of thing you might be thinking about is a cooper vane, but I don't think any aircraft have those on the cockpit windows.

The QRH on the EMB-145 for both windscreens cracked and no visibility is to don the smoke goggles, open the window and stick your head outside to land.  Glad I never got to try that one.

Opening a cockpit window is also a step in some QRHs to remove smoke from the cockpit under certain conditions (i.e. If nothing else is working & it is getting too thick to see the instruments). Depressurizing is accomplished first, along with slowing down. The 2 airplanes I've seen that as a checklist branch, didn't list any max airspeed for it. YMMV.

What happens when you open the windows at Mach .8 -- cruising speed in a 747?

@SargunDhillon You can't. (re read the first sentence of the answer)

Apparently the pilots of ET-363 on 2020-01-09 opened the cockpit window in flight to clean part of the windscreen from the remains of a locust swarm [1]:

The windscreen wipers were not able to clear the windshield anymore.
  The crew went around, climbed to 8500 feet, depressurized the
  aircraft, opened the cockpit side window and cleaned the windscreen by
  hand. The same happened on second approach to Dire Dawa. The crew
  again climbed to 8500 feet, cleaned the windscreen by hand again and
  diverted to Addis Ababa.

The linked page contains a picture of the windscreens after "hitting" the locust swarm and the partial cleanup operation.
[1] http://avherald.com/h?article=4d1de8cc&opt=0

It depends on the airplane, and there are speed limits on the ones that can be open.  The windows on mine can be open up to 140 knots, but that is barely flying speed so it's really not practical.
Naturally, you can't be pressurized if you have a window open.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Can you fly a plane in a wind tunnel?
There are very large wind tunnels out there. Wouldn't it be very efficient to test new airplanes flying them "on the spot" inside of these tunnels? That is, in free flight - not mounted to a pylon? One could presumably omit the test pilot and remote control them, get excellent visual feedback and have a completely controlled environment. Has this been done? If not, why?

the pilot sneezes and jerks the yoke-> the plane drops into the ground while there is 800 kmph winds pulling debris back into the wind tunnel exhaust cause quit a bit of damage

There have been tests of real aircraft in wind tunnels, with a pilot sitting in the cockpit. But in all cases the plane had been tied in place with strings. Trimming the lift and especially the thrust in all phases of the test is really impossible.
The Messerschmitt 109 was tested in the French Chalais-Meudon tunnel in 1940, the Bell P-39 was tested at Langley, where the top speed could be improved from 340 to 392 MPH, the P-51 was tested at Langley in 1943 like most small military planes of that period, and lately a stealth demonstrator made by MBB was tested in 1984, in most cases with the pilot in place. These are the ones I know; there were certainly more.

@Federico: Free flight in a wind tunnel is impossible. That's why I wrote "in all cases the plane had been tied in place with strings". The forces on the strings (actually steel cables) were measured to get an idea of the forces involved.

ok, i see that. deleting my comment

It would actually miss the point of wind tunnel testing. A free flying model could only be subject to air stream in speed and direction so that the forces are balanced. A fixed model on the other hand can be subject to air stream of any direction and speed and the forces measured. It is important to measure the forces under those conditions too.

Could you? Yes, probably, but it would be very difficult due to the very limited space. You would have to have a huge airflow in excess of 50 knots for a small aircraft, and you could not simulate any motion fully, such as takeoffs rolls. You could also not test stalls and other manoeuvres. I think the main reason against this is that this is simple areas of flight dynamics that can just as well be done with computational fluid dynamics on a computer for a fraction of the effort and cost.
I don't think it would be safer either. It's a very confined space, and you couldn't cut the airflow very quickly, so it's probably more dangerous than flying outside with unlimited space and a stable airflow.

You certainly could fly a completely assembled aircraft in a sufficiently-large wind tunnel -- at least in theory (theory is an awesome place - everything always works there. When I retire I'm moving to theory).
In reality there are lots of drawbacks which have already been pointed out, but there's one that hasn't been yet: Wind tunnel testing is traditionally done with scale models, and even then it's not "cheap": It takes a lot of power to move wind through a tunnel at high speed, and scaling this up to a full size airframe - even small-airplane size like your typical Cessna or Piper trainer - is cost-prohibitive since you would have to build the entire plane and then pay to blow high-velocity air over it.
(There are wind tunnels at this scale though - at least one. NASA spent a lot of money on it, and then Boeing and Airbus came out with their new super-jumbo planes which don't fit!)
It's also worth pointing out that the kind of fluid dynamics modeling that used to be done with wind tunnels and smoke trails is now often done with Computational Fluid Dynamics (CFD) software. Cheaper, Safer (no risk of parts blowing off and bouncing down the tunnel), and more accurate in many regards -- but nowhere near as much fun to watch :)

Yes you can. Yes it has been done. And yes people are still doing it. The caveat being that most (all?) of the tests are done with scale models rather than full size planes.
Free flight wind tunnel tests are done for different reasons from static mounted tests. Where static mounted tests are done to collect measurements of forces acting on the aircraft/part, free flight tests are done to understand/confirm the stability of the aircraft.
Flying a model plane in such confined spaces is very difficult and typically the plane will tend to wander around in the wind tunnel. As such, the data that you can get from a free flight test is very limited.
Due to the difficulties of doing the test and the limited amount of data you can get from it most new plane designs don't go through such a test. Instead, what typically happens is that the design goes straight to a radio controlled scale model that is flown outdoors to study its stability. However, when trying out new ideas that has not been developed it is still worth doing the stability tests in a controlled environment - in a large wind tunnel.
Here are some old videos of free flight wind tunnel tests (these come from a time period where the behavior of delta wings were not yet fully understood):
https://www.youtube.com/watch?v=OGmigdhxMRw
https://www.youtube.com/watch?v=aDIQc3-umf4
Here's a more recent video of a free flight wind tunnel test of the Blended Wing Body:
https://www.youtube.com/watch?v=B7zMkptajMQ

these are models, not planes.

@Federico: Model planes

it's still not a plane where "you can omit the test pilot"

Actually, it's exactly the OP's statement of omitting the test pilot and having the plane controlled remotely that made me post this. Some of these models are larger than a Cri-cri. So they're definitely large enough to be considered full airplanes. Only, the final product is usually intended to be much larger still.

No, you cannot fly a plane like that.
Problem is: propulsion is missing. Once you expose a plane model to an airstream, the airfoils (wings) start producing lift but also drag. In real world, an airplane requires propulsion to overcome the drag (induced drag,parasite drag,..) in order to move forward.
The wind tunnel airplane model would just lift-off and fall behind, there would be no chance to establish a stabilized flight attitude where propulsion equals drag and lift equals weight. Such a stabilization is required to seriously start measuring. That's why the models are strapped down to a pylon or whatever. Measuring results can therefore also be reproduced (certain fixed AoA's at certain airstream speeds etc.)

I was thinking with engines on.

Ok, with engines on (probably small jet engines or electric propellers) the model would be flyable in the airstream, for fun reasons. But consider how unsteady model airplane fly - impossible for serious measuring. I guess controlling it by an autopilot would rise costs unaffordably - though being an interesting idea :-)

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How are special flight paths coordinated with ATC?
I assume they have to enter a flightplan for this or do say just say "it's a test, please clear airspace for us around the complete US"?

Still flying and completing the right wing.
I would appreciate it with a 747-8, harder to draw :)

"please clear airspace for us around the complete US" well, it does not seem so, as plenty of airplanes are flying around it

I see what they did there...

Is that for real, or are they just feeding bogus data to the system somewhere?

Closely related, perhaps a dupe?

I think it is real, at least the flight-number seems to be used by Boeing in the past. Probably just funny marketing and a demonstration of range.  http://www.airteamimages.com/boeing-787_N7874_boeing_203670.html

Can you tell what it is yet?

@Federico: Thanks for FAA-Tag, obvious choice.

@GdD it's a 787 flying a path that follows the 787 shape. (boeinception)

@SQB why they would?

This type of flight would require planning, so I doubt anyone who planned to do something like this would first fly from Washington state clear across to Wisconsin before beginning the design.  Funny though.

the complete path (and flight reason) https://twitter.com/flightradar24/status/893098349733322756

Thanks! So the reason for this demonstration are the new Trent 1000 TEN engines.

Rules for ATC in the US are laid out in FAA JO 7110.65.

The primary purpose of the ATC system is to prevent a collision between aircraft operating in the system and to provide a safe, orderly and expeditious flow of traffic, and to provide support for National Security and Homeland Defense.

It's up to ATC to use their best judgment as to how to accommodate the requests of the pilots while keeping the system safe and expedient for everyone. Pilot requests can always be denied, but of course the pilot has the ultimate responsibility for the safety of their flight.
Since ATC is specifically required to support National Security, the military already has reserved areas charted, called military operations areas, or MOAs, and Restricted Areas. The military has priority in a MOA, and when Restricted Areas are in use non-military aircraft need special permission to fly there.
For civilian flights, they are less likely to get a completely reserved area. ATC needs to know where the aircraft will be so they can keep them separated from other traffic. If pilots want a block of airspace for testing, where they can turn, climb, and descend without asking permission every time, they typically need to find some airspace where they can stay out of the way of other aircraft. Companies like Boeing may have agreements with ATC about certain areas that are available for this kind of usage, often out over the ocean
For special tests like the one in the question, the pilots have to plan out their route. The filed route uses GPS waypoints to complete the pattern:

KBFI SEA NORMY J70 MLP GTF 4632N/08706W 4626N/08908W 4301N/09715W 4352N/09907W 4358N/09958W 4306N/10033W 4245N/09958W 4229N/09834W 4122N/10101W 4254N/10552W 4312N/10730W 4314N/10848W 4302N/10919W 4235N/10907W 4157N/10820W 4112N/10654W 3932N/10210W 3717N/10133W 3757N/10243W 3803N/10323W 3702N/10401W 3633N/10320W 3604N/10117W 2827N/09937W 2652N/09820W 2814N/09844W 3438N/09829W 3538N/09819W 3745N/09715W 3610N/09249W 3533N/08953W 3148N/08837W 3126N/08754W 3503N/08731W 3457N/08616W 3539N/08713W 3809N/08411W 3820N/08458W 3642N/08915W 3804N/09148W 3935N/09604W 4143N/09442W 4230N/09354W 4601N/08829W 4631N/08706W KBFI

The pilots must stay on their cleared routing and ATC will do their best to accommodate them. Of course if safety becomes a concern ATC may have to deviate them from their pattern. But knowing the flight path ahead of time, ATC should be able to have other flights in the area out of the way without much trouble.
This flight in particular was done overnight, when air traffic is lightest, which would have made separation much easier. Also, a lot of the path is in the western US, which also has less air traffic. Towards the end of the flight, once more fuel was burned off, the flight climbed to FL400 and higher which would have taken it above most other traffic. All of these factors would make ATC more likely to accommodate this sort of strange routing.
There are many other examples of this sort of thing:

787 and Boeing
logo
737 MAX
747
747-8
Seahawks
Gulfstream
Cessna

Thanks. Comparing with the other examples from your list, Boeing invested this time more effort for a fine picture :)

@JonathanWalters thanks, I edited to make it more accurate.

Developing remote sensing devices, there have been many times that I have had to fly specific routes at specific speeds. Normally I pre-coordinate with each ATC facility and nearby towers.  A cover letter, a route plan, and any additional data covering the specifics of the test are included. If the customer is a governmental agency, I will often mention that.  The day before, someone calls a supervisor at each facility to remind them.  The same day, usually, but not always, a call is made prior to the flight.
There are some procedures in controller handbook (US) but the point is that clear communication has always gotten priority handling, except when we conflicted with Air Force One.  We will always offer to yield to lifeguard flights (and have to anyway).  After doing this type of flying for 35 years, I cannot think of one time that what was requested didn't get granted.  That includes controllers stopping arrivals and departures at DCA for 5 minutes on one test.
Some of the flights were National Security flights, but most were not, and reasonable and well communicated requests have consistently received excellent support from ATC.


text:
What is a battery pod?
On a manual in school was written: 'The fuselage battery pod must be made in a metal to improve the impact resistance'.
What is meant with battery pod here?

Is this about GA planes? Some specific airliner? Military? What's the book title and author? "On a manual .. was written" makes it sound like graffiti, confirm if it is typeset or handwritten?

The definition of pod is: A detachable or self-contained unit on an aircraft, spacecraft, vehicle, or vessel, having a particular function.
Therefore a fuselage battery pod would be a detachable or self contained unit that has the function of containing the battery.

Most vehicles with a battery have a means to contain the battery to restrain it from moving.  Some also include a method to vent gasses, and/or contain a battery fire.  I have heard them more commonly referred to as a battery "box", but "pod" would be an acceptable term as well.
If you do a word search for "aircraft battery pod" you can see some examples.  If your manual is having to do with an EV aircraft with batteries in the fuselage then presumably the requirements might be more stringent than a battery forward of the firewall used to start an internal combustion engine.

If you want more detail than this you will need to offer more context from the manual you mention in your question.

@757toga, thanks and good info!  I added a tweak to my answer to include fire...


text:
High performance endorsement
If I am a Commercial multi rated pilot with high performance and CFI. But not CFII or MEI, can I give a high performance endorsement to another commercial multi rated pilot in a multi engine?
The thought being since we are both multi rated, an MEI is not needed. But I am not 100% certain on that.

I'm just curious, how is it possible to become a commercial multi-engine rated pilot without a high performance endorsement?  Is there a CFR that specifies HP of each individual engine must be >200?  (I would have presumed that a twin with a couple 120s would be considered 200+HP, and therefore high performance...)

@757toga, yeah I see that, and while it's clear enough for a SE, it isn't how any "normal" person would write a reg for ME.  For a multi one would chose an example such as "an airplane with any engine of more than 200 HP." or "an airplane with engines of more than 200 HP each."

No, you can't.
FAR §61.31(f) states (emphasis mine):

(1) Except as provided in paragraph (f)(2) of this section, no person may act as pilot in command of a high-performance airplane (an airplane with an engine of more than 200 horsepower), unless the person has -

(i) Received and logged ground and flight training from an authorized instructor in a high-performance airplane, or in a full flight simulator or flight training device that is representative of a high-performance airplane, and has been found proficient in the operation and systems of the airplane; and
(ii) Received a one-time endorsement in the pilot's logbook from an authorized instructor who certifies the person is proficient to operate a high-performance airplane.

FAR §61.1(b) defines "authorized instructor" as (emphasis mine):

(i) A person who holds a ground instructor certificate issued under part 61 of this chapter and is in compliance with § 61.217, when conducting ground training in accordance with the privileges and limitations of his or her ground instructor certificate;
(ii) A person who holds a flight instructor certificate issued under part 61 of this chapter and is in compliance with § 61.197, when conducting ground training or flight training in accordance with the privileges and limitations of his or her flight instructor certificate; or
(iii) A person authorized by the Administrator to provide ground training or flight training under part 61, 121, 135, or 142 of this chapter when conducting ground training or flight training in accordance with that authority.

Because you're not an "authorized instructor" in a multi-engine airplane, you can't give the training required by §61.31(f)(1)(i), nor can you use a multi-engine airplane to "certify" another pilot's proficiency under §61.31(f)(1)(ii).
Your creative thinking seems reasonable on the surface, but the verbiage is pretty clear here, and the FAA and courts are known to interpret the regulations very conservatively. You could always ask the FSDO for an official interpretation (if you do, please come back and post the answer here for us!).
Until then, I suppose you'll need to find either an MEI or a single to fly in.

Negative.  See §61.195(b)(1-2)

Except as provided in paragraph (c) of this section, a flight
instructor may not conduct flight training in any aircraft unless the
flight instructor:
(1) Holds a flight instructor certificate with the applicable category
and class rating;
(2) Holds a pilot certificate with the applicable category and class
rating; and
(3) Meets the requirements of paragraph (e) of this section, if
applicable.

This includes logbook endorsements as well for particular aircraft category and class.
Now it is possible to give the other person a high-performance endorsement if the training is conducted in an aircraft category and class listed on your flight instructor certificate.  As I understand it, there is no distinction between a high-performance, single engine airplane in a high performance, multi-engine airplane in re to training requirements to meet §61.31(f).


text:
Are lessons available for FlightSim X?
I have Flight Simulator 2008, and there were some really good lessons for student pilots.
Are there flight lessons in FlightSim X, either part of the software, or available from external sites?
The FSX Learning Center shows some, but it seems you can't use them.

FSX has lessons. See the Learning centre.
You have to scroll through the text, and then you can fly some lessons.


text:
Can a small GA plane maintain level flight with a significant nose-down attitude?
Consider a small, one- or two-seater motor GA aircraft, something like a Cessna 152 or similar, designed for level flight at roughly neutral pitch.
It's certainly possible to fly such an aircraft in a nose-high attitude while maintaining altitude, by careful use of pitch and thrust. I'm not sure I'd want to do that for any significant length of time, but as long as the angle of attack is kept below the critical angle for the current aircraft configuration, I can see no aerodynamic reason why it can't be done even in the general case.
But is it possible to fly it in a significant nose-down (say, several degrees or more) attitude while maintaining altitude?
My gut feeling says no; no matter what else you do with the aircraft in such a nose-down attitude, you're going to be losing altitude. But I've been surprised before, so: is there a way?

well - gliders do that while flying in the thermals :)

@gusto2 you should make that comment into an answer

@gusto2: It can also be done in a light plane if you happen to get into an area of wave lift.

Similar to what @gusto2 said, I recall being on a student solo cross country flight in a C152 and entering a significant thermal. I had to reduce power and pitch down a bit below the horizon just to maintain altitude until I exited the thermal.

Although hardly a small aircraft, you might find it interesting that a B-52 routinely climbs (e.g., immediately after take-off) with a visibly nose-down attitude.

It depends on the angle of the wing chord line relative to the fuselage and also on the current vertical component of the wind. A normal light GA airplane will not be able to fly level with a negative angle of attack, but it can fly level with a nose-down attitude if the wings themselves are pitched upwards relative to the aircraft fuselage and/or if the mass of air through which the aircraft is flying is rising.
As user2209250's answer alludes to, dropping the flaps is one way to increase the pitch of the wing chord line relative to the fuselage, possibly allowing the wings to have a positive AoA even while flying level with a nose-down attitude. Especially for larger flap extensions, many airplanes will likely require a nose-down pitch in order to maintain level flight with a full thrust setting.
Of course, most airplanes are designed such that you will not be able to maintain a positive angle of attack with a very steep nose-down attitude in level flight in a non-rising mass of air, but shallow nose-down attitudes are certainly possible.

I may have misunderstood the question but I think the answer may be... flaps. Wing flaps will increase the lifting ability of the wing and at a constant airspeed the nose will need to be lowered to maintain a particular altitude.

Beyond a very small angle, a nose-down attitude means a negative AoA, and lift will be negative.
A nose-high attitude is different, because lift will be always positive, even beyond the critical stall angle, and for some airfoils, that lift may be quite significant...

As long as the wing (the whole aircraft) has lift, theoretically, with higher speeds the pitch should go lower and lower.
This means with full thrust, keeping the altitude constant, time will show how nose-down the aircraft can go.


text:
Who decides what measurement units are used for altitude, and why is there no standard?
I know that some countries (Russia and China for instance) use meters to measure altitude while the rest of the world uses feet. Why isn't this standardized around the world?
I guess all modern cockpit instruments nowdays offer both unit system measurements, but this must be creating some confusion for pilots.
Who decides which measurement units should be used for aircraft altitude? The airlines? ATC? Each country?
Why are both units of measure used?  Are there any pros or cons with using meters?

FWIW, my impression of whether countries use feet or meters is a legacy of the cold war. Soviet bloc used meters, others feet. A bigger problem for pilots, in my opinion, is the differing transition altitudes between countries.

Another interesting aspect to consider is precision... there's 3+ feet per meter, which means an altitude given in feet can be more precise than one given in meters (assuming no decimal point).

@JeffBridgman: Why would anyone assume "no decimal point" when there are concerns about a lack of precision? Isn't that the same as saying "Feet cannot be used for measuring anything more precise than 10 feet, assuming that we don't use the last digit."?

By the way, in English it's "metres". A meter is a device for measuring something, a metre is a unit of length.

@MarkyMark By the way, "English" usually means American English on SE sites, you might want to be specific and say "British English". ;) Or "Australian", obviously. :D

@falstro and why do we use the American name for something that most Americans for some reason refuse to use?

Unfortunately, countries tend to want to decide themselves how stuff is supposed to work once you're within their borders. That's why we have different rules and laws, and when you go somewhere else in the world, you might need to know some of the differences.
In England they drive on the wrong side of the road, imagine that! :)
In order to have things run smoothly in something so utterly international as aviation, the organization called ICAO (International Civil Aviation Organization) where most countries of the world are members, dictates the rules, (I believe they are) called the ICAO drafts recommendations which the member states should incorporate into their respective laws and regulations. If they choose not to, they need to inform the ICAO of such deviation, don't know exactly what happens then, but I believe the idea is to at least let everybody know there's a discrepancy.
The ICAO Annex 5 specifies units to use, including units for altitude and actually specifying meters as the primary unit, with feet being accepted as non-SI alternative. Why on earth you'd want to go against the majority on this I don't know, perhaps due to the fact that it's an SI unit and they want to be as much SI as they can. So it's basically up to each country how they want to play it. Most countries stuck with feet.

In England, we drive on the correct side of the road.  It's you Americans who copied the French in driving on the wrong side of the road. [Comment intended to illustrate how different countries make their own minds up]

IIRC, in England people drive on the side of the road which was once considered the "most convenient" side to ride horses from. Right or Wrong, is entirely perspective.

In response to the pros/cons of feet vs. meters, the big advantage that feet have over meters, is that it allows you to use nice human-memorable numbers for cruising altitudes.
In the US, we generally use 500ft for visual separation, and 1000ft for separating IFR traffic from other IFR. This translates to roughly 150m and 300m respectively. This means, we can explain IFR cruising altitudes as odd-thousands going east, and even thousands going west (up to FL410).
If this were in meters, you'd have to try to explain that going east it's 300m multiplied by odd numbers, and west it's 300m multiplied by even numbers. It's certainly not impossible to figure out in your head, it just isn't as quick and easy. Unfortunately 100m is considered too little separation, and 500m would be an inefficient use of airspace (over-separation), otherwise there might be more of a global push to use meters.
Interestingly, although Russia does use meters, they have actually adopted the international "Flight Levels" (i.e. "climb and maintain FL350" which would be equal to 10650m), so now international flights do not have to change altitude when crossing the border into Russian airspace. However, I believe this is not true for other countries which use meters, such as China, where the separation is typically 300m.

I have heard the use "FL X meters", which I suppose is simply "X meters" of pressure altitude, do you know by any chance?

@roe I haven't heard that, so I'm not sure.

@roe That's correct.

If the system had been set up with metric units from the beginning, isn't it conceivable that 250 m of separation would have been found sufficient, such that one could have xx000 m and xx500 m in one direction and xx250 / xx750 m in the other? Sounds fairly quick and easy to me.

@HenningMakholm possibly, but even the countries which have always used meters don't use 250, they use 300 (984 feet).

The only reason imperial units are used at all is because of the US' historically important role in aviation. Changing aviation over to metric at the point would be an interesting challenge.

@BretCopeland They (metric-based countries) don't use 300m, they use the international altitude separation standard. This standard has been set to a given value because of historical reasons.
The fact that its value is about 1000 ft/300 m is irrelevant to why they use it.

Oddness or evenness is preserved when multiplied by 3: 300 x (odd number) = (other odd number)-00; 300 x (even number) = (other even number)-00. Quick and easy in my head.

As to feet being the best measurement for height, what utter nonsense! Prior to WW2, all metric countries flew in meters. That changed after WW2 with America dictating what happened on this planet. Unable to convert to the metric system for one reason, big money that has so far thwarted all efforts to accomplish this important task.America forced the almost 80% metric world to fly in stone-age measurements called feet.Well so much for democracy! Maybe China will eventually do the same and force America to go metric! Sure a drastic step, but a well-deserved one!

Now if only the metric folks didn't utterly fail their mission in the two most critical pieces: time and angle (which gets used for geocoordinates). Qucik, tell me, what is 1000 ft/min in knots. Now, what is 5 m/s in km/h. Better? Not… Without decimal system for time and angle, much of the benefit of metric is lost here (the examples are the units used for vertical and horizontal speeds in their respective systems).


text:
Can pilots change the callsign shown on tracking websites mid-flight?
Today I viewed the following flight on FlightRadar24 website. It show a flight with a callsign of 'BLEED' and with the destination missing. Is this a problem with the website or can an aircraft change its transponder data to show such a callsign?

And this is a news report item about this flight:
https://www.jpost.com/Breaking-News/Flight-enters-Israel-from-Turkey-with-call-sign-BLEED-573889

Yes, a pilot can change this in-flight, just as they would have entered the data when on the ground before the flight.
On the A320, this is done from the FMGS (Flight Management and Guidance System). To do this, the pilot presses the DATA key on the MDCU (Multipurpose Display and Control Unit) keyboard. This brings up the following display:

And then selects the A/C STATUS page, which allows them to change the code (call sign/flight number):

This can be changed in flight by the pilots at any time. This information is sent to the ADS-B and other data-link systems that show up on radars and ultimately sites like FlightRadar24.

Thanks for detailed the answer, Ron. Can a pilot change the callsign to any value he/she wishes. Are there air traffic rules for setting callsigns? and do you know what 'BLEED' callsign means?

I do not know what the BLEED callsign means, but yes, a pilot can change it to anything they wish. What it should be is the flight number though, and ATC will usually get upset if you change it mid-flight (because it shows up differently on radar).


text:
TFR based on an invisible VOR?
A new TFR was recently published, which references the Riverside (RIS) VOR/DME.
When I look at the relevant chart in SkyVector, I don't see such a VOR in that area.
When I put the ID "RIS" into SkyVector, it takes me to an intersection outside London, UK.
PilotNav has the info, but that took a lot of searching.
How is one meant to interpret this TFR if the nav aid is so hard to find?
Why didn't they use bigger and easier NavAids like MCI or ANX, which are not far away, and clearly depicted on the charts?

Update!After I brought this to the attention of the local offices, they canceled the TFR and issued a new one expressed in terms of the MCI VOR, which makes a lot more sense.    The FAA was incredibly responsive and helpful!

RIS was discontinued in September 2017. Maybe they just copy pasted an old TFR without checking.

Thanks @fooot.  Confirmed here as well: http://www.boldmethod.com/learn-to-fly/navigation/the-faa-is-shutting-down-308-vors/

This would be an good thing to call and ask them about; Kansas City Center is the responsible ARTCC. It certainly looks like the TFR is based on a decommissioned and uncharted navaid, which shouldn't be the case.

I sent a note to the local FSDO via their webform.   I may try to contact them in other ways.

The secret service owes you one!

See if the Secret Service will let you take Air Force One up for a few trips in the pattern!  :)

After I brought this to the attention of the local offices, they canceled the TFR and issued a new one expressed in terms of the MCI VOR, which makes a lot more sense. The FAA was incredibly responsive and helpful!
They didn't explicitly say it was a mistake, but I think they decided it was better to use an operational VOR.
(however, a couple weeks later, they referenced the RIS VOR again in a NOTAM.)

ForeFlight shows it on the airport at Wheeler Downtown.

Garmin Pilot has it as well.  But isn't the Paper Chart the authoritative source?

Probably not anymore, actually.


text:
Why does this A380 power outlet give 400Hz power?
Recently I found this image from the internet that shows a power outlet in the Airbus A380 and it has been labelled "115V - 400 Hz 1kVA max".
All of that makes sense apart from the 400 Hz part. Why is that? Wouldn't it be more useful if it provided 50 Hz or 60 Hz electricity that most appliances use?
What's the use of this outlet?
Is it because of something related to the APU generator?

Related: Why do aircraft use 400 Hz AC instead of the 50 or 60 Hz of wall outlets?, How common are 400Hz supplies in aircraft? and How does the A350/380 operate on Variable Frequency AC generators?

Is there a standard wall socket under there? All the photo shows is a cover plate, not a power outlet.

Because that's what planes use.

The use of the outlet is for vacuum cleaners for the cleaning crew.
Traditionally, large planes used 400 Hz power. Therefore infrastructure, namely ground power supply units and the vacuum cleaners that cleaning crew use are designed for 400 Hz.
The A380 uses a variable-frequency AC system where the frequency drifts from 360-800 Hz depending on engine speed. However, to remain compatible with existing infrastructure, busses stay at 400 Hz when connected to ground power.

Aircraft use 400 Hz AC because it's more efficient and makes for lighter transformers than lower mains frequency. But the higher the frequency, the more losses with distance. There's no good reason to use 50 or 60 Hz on a plane, except for passenger convenience, since the distances are all quite short. International power lines tend to use DC to minimize the losses.
Why don't planes? DC is harder to use: you need complex power electronics with controller to efficiently convert DC-to-DC. They've become common in the PC era, and are far lighter than transformers, but modern aircraft have become standardized before that (the 737 is from the 1960s). DC-DC is the future, but it's still the future.
While at that, most modern electronics use switching mode power supplies, which don't care much about the frequency. They convert AC to DC first, and can even run on direct current. Most modern power supplies will work fine with 100V or 300V, 0 Hz or 50 Hz or 400 Hz. Many flight crews routinely use these outlets to charge their laptops and phones. So 400 Hz works just fine.

Disclaimer: Don't try this at home (not that you can), and especially don't try this on a commercial flight. It may only be 1 in 100 devices that won't work on 400 Hz, but in-flight isn't the time to check if you've drawn the short straw.
The reverse also doesn't work. Do not try to power airplane equipment from a 60 Hz outlet. 400 Hz transformers are smaller than 60 Hz ones, and will overheat or short the power input if fed 60 Hz under load.

This may be true for most aircraft, but the A380 doesn't use 400 Hz AC. It uses variable frequency generators.


text:
Moment Created by an Airfoil and Stability
I am working on designing a remote-controlled flying-wing aircraft and am learning about important configurations and factors in the design.
I have been going through this page because it seems like a pretty useful resource, and I have seen it referenced a few times in other posts. Upon going through it, however, I ran into something which has generated a question about the moment generated by an airfoil, and I believe it relates to my understanding of the aerodynamic centre.
For a given airfoil, I know that, as the angle of attack changes, the center of pressure shifts along the chord line. I also know that (within an operating range avoiding stall nonlinearities) the magnitude of the lift force that acts at the center of pressure increases too.
This leads to my current understanding of the aerodynamic center. If you pick an arbitrary point along the airfoil's chord and calculate the moment generated by this lift force, it will likely change as the angle of attack changes because both the moment arm (distance between an arbitrary point and center of pressure) and magnitude of the force change. The aerodynamic center is, therefore, the point at which the moment does not change with respect to the angle of attack.
My confusion then comes from the diagrams shown on the provided website and elsewhere indicating that the lift can be said to act at the aerodynamic center. I can accept this fact generally, but I am therefore confused about how we can say that it also generates a moment about this point. This is particularly relevant to the website I showed above: how can there be a moment generated by the lift force about the center of mass while also being a moment generated at the aerodynamic center? My understanding is that this moment about the aerodynamic center IS generated by the lift force.
I apologize for making this post so long for what is likely a simple question, but I wanted to explain my current thinking so that hopefully someone can point out the error in my reasoning. Any help would be greatly appreciated.

software documentation link   and program to accompany link     You can create a reflexed airfoil, change angle of attack, see what happens to flow over the airfoil, examine changes in lift and pitching moment.

When all else fails, try a delta wing.  Think about it.

Maybe I should have a word with Martin Hepperle, but the way he displays the force is how you will find it in the literature, too.
Please note that in addition to the lift vector at the neutral point, he also displays a moment (symbolized by a circular arrow), and together the varying force and the constant moment are physically correct to describe the full lift forces.
To avoid more confusion about the center of pressure and the neutral point, here are the main aspects:

The neutral point / aerodynamic center is fixed over angle of attack
All lift forces can be summed up in one force acting at the neutral point plus one moment which is constant over angle of attack.
The center of pressure / center of lift is the resulting point at which the summed up lift forces act.
The center of pressure changes with angle of attack for cambered airfoils.

Thanks for your response, that was my understanding from the diagrams and I appreciate your clarifications.
I have a follow up question however: is constant moment an artifact of assuming that the lift force always acts at the aerodynamic center? I am otherwise confused about how a moment would be generated that would be different than simply the effect of the lift force about the true center of mass of the aircraft.

@Toogoodoo Follow the link in the third bullet point. If that does not help, please post a new question and describe precisely what is so confusing. Answering in comments leaves little space for explaining broad questions.

the link answered my question exactly, thank you!

Here there's the usual misunderstanding of trimming vs. stability at work.
An airplane is trimmed if all moments (and forces) acting on it sum up to zero. That's simple. Anyway it is stable if: when, for any reason, the AoA increases then the moments decrease in order to consequently decrease the AoA and bring the airplane back to its trimmed position. So, to be stable, an increase in AoA must be counterbalanced by a decrease in moments, so that their ratio is negative.

For a flying airfoil/wing the math is easy since we only have:

the mass acting in the CG
the lift acting at the aerodynamic center (aka ¼ of the chord for thin airfoils at subsonic speed) and
the aerodynamic moment:

(ubiquitous picture by NASA modified by me)
The total pitching moment $M$ in respect to the CG is therefore:
$M=L(x_{cg}-x_{ac})+M_{wing}$
and if we set it to $0$ we get the conditions for trimming. Instead, the stability equation is:
$\frac{∆C_M}{∆\alpha}=\frac{∆C_L}{∆\alpha}(x_{cg}-x_{ac})$
and if we set it to $<0$ we get the condition for stability. $∆$ here is simply the mathematical symbol for "variation". Note that the term $M_{wing}$ has disappeared since its variation in respect to AoA is normally negligible. In order for this equation to be negative, we readily see that $(x_{cg}-x_{ac})$ must be negative i.e. the CG must be in front ($x_{cg}$ smaller) of the AC. This is a general rule valid for any flying airfoil/wing, no matter if it has a "normal" or a reflexed camber.
Now to the trim equation: as just seen, the first term $L(x_{cg}-x_{ac})$ is negative in order to make the airplane stable and therefore the second term $M_{wing}$ must necessarily be positive to have a total sum of $0$. And here is where the reflexed camber helps us out: those airfoils normally have a positive moment coefficient, while a "normal" cambered airfoil has a negative moment coefficient:

This plot (source) gives the moment coefficient for several airfoils with more or less reflex: the yellow one would be a good candidate for your flying wing.

If lift does not act at CG, how is the aircraft trimmed?  What you need in your diagram if another torque in the opposite direction resulting in a net lift (center of pressure) at the CG.

how a moment would be generated that would be different than simply the effect about the true center of mass of the aircraft

Well, it wouldn't be if the center of mass were at the aerodynamic center but ...

Let's not forget what the rest of the aircraft does to the
aerodynamic center or "neutral point"

By shifting the center of gravity ahead the neutral point, we
can now create the interplay between wing torque and "tail"
torque (around the CG) in order to create static stability.

Weight can be moved forward and/or tail lift coefficient
and/or area can be increased to increase stability

When this is done, the AC or neutral point moves rearward.

the "neutral point" thus serves as a reference in design, not
where actual forces act around unless ... go to beginning of answer.

Would the downvoter please explain what is wrong with this answer?


text:
How do pilots detect and respond to windshear while landing and taking off?
How does wind shear affect aircraft while landing and taking off? How do pilots detect that they are encountering wind shear and what would they have to do to prevent it from turning into a bad situation?

The most dangerous form of windshear for planes is the microburst. This is a downdraft that after it hits the ground spreads out in all directions. It is dangerous particularly for planes low to the ground (on takeoff and landing)
When a plane coming in for a landing approaches the microburst it will enter a headwind and see and increase of airspeed and lift, the inexperienced and unsuspecting pilot may then reduce engine power to slow down and keep himself aligned. After the plane passes through the burst it will enter a tailwind decreasing lift which may cause the plane to crash into the ground short of the runway.
To prevent crashing the pilot would need to keep power and possibly abort the approach to wait out the burst.
Detecting windshear from the ground is done with doppler radars (TDWR) and multiple wind sensors (LLWAS) which can detect the changes in wind which will be relayed to pilots in accordance with regulations (3-1-8).
All turbine powered airplanes used in §121 operations, except for turbopropeller powered airplanes, must have a windshear detection system installed, this is detected in one of 2 ways, using the onboard weather radar (predictive) or using the wind sensors on the aircraft like the angle of attack and airspeed (reactive).

don't forget that the downdraft of the microburst itself also affects the airplane to compound the problem

While this answer addresses microbursts, which are certainly the most dangerous, it doesn't address the more common types of windshear which pilots encounter on a regular basis.

The reactive windshear algorithm uses both air data and inertial data to identify the presence of windshear.

Windshear recognition and recovery, both during takeoff and landing are regularly practiced in simulators. Recognition includes a sudden loss of airspeed or a sudden increase in airspeed (probably to be followed by a sudden loss). Recovery (at least back when I was flying) included going to max power while bringing the nose up until stick shaker activation, which condition you would fly in until through the shear.

As soon as uncommanded: speed  deviation of 15-20kts. Vertical speed deviation and glide slope deviation of 1 dot and if EGPWS incorporates windshear call outs and Flight Director guidance for windshear recovery; SIMULTANEOUSLY:
DISCONNECT AUTO PILOT
MAX THRUST
FOLLOW FD GUIDANCE (or WINGS LEVEL MAX PITCH TO STICK SHAKER)
DO NOT CHANGE CONFIG(EXCEPT SPEED BRAKES  CLOSED IF THEY WERE OPEN)
ADVISE ATC
ADVISE CABIN

would you happen to have a source for that? it seems to be quoted from somewhere.

No..from my own experience and reading of various aircraft flight manuals which I was was qualified to fly.

In that case, it would probably be best to write this answer in ordinary English instead of writing it in the style of a flight manual. As your answer is written, people who see your answer are going to think it's a quote from one particular aircraft's manual.


text:
Can propeller driven aircraft sustain speeds at or above Mach 1?
Has any propeller driven aircraft ever achieved and sustained supersonic speed? If not, why can't propeller airplanes achieve that speed?

In controlled horizontal flight?

@mjs yes.in a steady controlled horizontal flight

Supersonic level flight?  No.
The fastest propeller-driven aircraft is either the turboprop-powered TU-114 with a measured top speed of Mach 0.73 or the turboprop-powered XF-84H "Thunderscreech" with a design top speed of Mach 0.9 and an actual top speed of either Mach 0.83 or Mach 0.7 (sources disagree).  The latter is an indication of why supersonic propeller-driven aircraft are unlikely: the continuous sonic boom coming off the propeller tips made the Thunderscreech the loudest airplane in the world.
The record for piston-engine aircraft is slightly lower, at Mach 0.71.

Why would there be a continuous sonic boom coming off the propeller tips? If it was turning fast enough with the tips supersonic and the hub subsonic I'd agree (some part of the prop would always be precisely at Mach 1) but in this case the entire prop would be supersonic wouldn't it?

@falstro: The sonic boom is not only occurring at Mach 1, but at all speeds above it. When a body travels faster than the sound, the forward-moving sound waves are compressed and will form a cone. When this cone moves over the ear of an observer, he will hear the pressure changes across the boundary of this cone as a sonic boom. Theoretically, a properly designed propeller will still work at supersonic speeds, but the efficiency will be so horrible that nobody has tried that seriously.

@PeterKämpf you are correct of course. The question still remains though, if the entire aircraft is supersonic, why would a spinning prop make more of a boom?

@falstro more of a boom? The Thuderscreech never went above mach as a whole system. The propeller turned such that the tips were above mach. As soon as they did so they were radiating a sonic boom. Each blade was. When a blade passed the plane (level/altitude/height of your ears) of your hearing you would hear it's boom, then when the next blade's boom came across your ears, you would hear it's boom. Many booms per second, which to you would "sound like" one long continuous boom, but in fact were waves of booms radiating out.

Compare my comment about the 'radiation of booms' to what happens when an entire aircraft passes through mach. One boom. As long as it was only the blades achieving supersonic speed, they would continue to radiate the boom.

@CGCampbell oh I'm not questioning that, I'm wondering why the speed of the tips matter when the entire aircraft is supersonic. The Thunderscreech never was, sure, but the answer says the latter is an indication of why supersonic propeller-driven aircraft are unlikely: the continuous sonic boom coming off the propeller tips, would the fact that the there's a spinning prop make it noisier than a jet?

@falstro - If you read the wikipedia article you'll see that the XF-84H's propellor tips were going supersonic even when it was on the ground.  Causing aaaallll sorts of havoc for ground operations.  The inability to get to a designated "supersonic" zone before unleashing a huge sonic boom seems like quite the show stopper.  Further, the sonic waves coming from the tips (when the rest of the craft was subsonic) appeared to mess with the aircrafts general stability.  I'd think those two reasons together are sufficient to explain that sentence.

According to Wikipedia:
"The tip of the propeller on many early aircraft may reach supersonic speeds, producing a noticeable buzz that differentiates such aircraft. This is particularly noticeable on the Stearman, and noticeable on the North American T-6 Texan when it enters a sharp-breaking turn. This is undesirable, as the transonic air movement creates disruptive shock waves and turbulence. It is due to these effects that propellers are known to suffer from dramatically decreased performance as they approach the speed of sound. It is easy to demonstrate that the power needed to improve performance is so great that the weight of the required engine grows faster than the power output of the propeller can compensate. This problem was one that led to early research into jet engines..."
So basically the performance drops so badly that you better switch to jet engines. In fact when designing the blades, a max tip Mach of ~.9 is a hard limit of design. The text continues to say that nevertheless some propeller aircrafts were able to approach speed of sound in a dive.
http://en.m.wikipedia.org/wiki/Sound_barrier

What if you had a jet that pushed the plane above Mach 1 and then turned on the propellers? Impractical, I know, but just for the sake of the argument?


text:
Is there usually vertical movement between the wing and fuselage?
Is there a slight movement in the point of connection of the wing with the fuselage of the Airbus plane in the event of flight and air turbulence?

Related: How is a wing joined to the fuselage? and perhaps: How strong is the A380 fuselage-wing joint?

While all structures have some compliance, for all purposes, no.  The wing-body join is going to be an extremely rigid set of fittings with numerous bolts attaching them.
The wing itself is quite flexible.  The wingtip will deflect substantially in flight and the deflection will change in turbulence.
The fuselage is also flexible.  In general, it 'hangs' on the wing -- the aft fuselage droops throughout flight, but also while sitting on the ground.  The forward fuselage is supported by the nose gear on the ground, but droops in flight.

Could also be Slats, Flaps, Ailerons, control surfaces might give the illusion of movement of the wing ?    Also, subtle movements of the cladding will magnify changes in reflections due to light, looking like additional movement that is quite microscopic ?


text:
What is this old pusher propeller aircraft?
I am researching the history of pusher aircraft and came across this photo. Any information or guesses as to its history? Country, designer, mfg, pilot, etc? It looks to me like perhaps a 1920's powered glider (looks like a wheel not a skid at the front but can't tell for sure) but that's a guess.
Update: I found another picture without comments of the same aircraft dated 1912 - so this is one of the very first attempts at flight. Which means it likely is not a glider but an experimentation with configuration. It does have a wheel at the front - not a skid.

Beware: searching through the FlightGlobal archive, the term 'pusher' does not appear until June 1913. Before then, the airscrew-behind form was simply known as 'propeller configuration'. Thus, this 1912 article does not refer to the Paulhan-Tatin Aéro-Torpille as a 'pusher', but merely notes that the propeller is 'disposed at the extreme rear end of the main body'. And likewise, the mystery aircraft probably will not be described as a 'pusher' in any contemporary sources.

I found two mentions of it, one was a design article written by Molt Taylor and his Aerocar...
"To our amazement, we found that a fellow by the name of Edson Gallaudet had built a shaft drive airplane way back in the 1910-1912 era which was twice as fast as contemporary airplanes! Gallaudet flew his Al and A2 Bullet models in the 120-130 mph speed range at a time when his fellow designers were happy to be able to fly 60 mph. And while they were still sitting out there on their wings with their pant legs fluttering in the breeze, Gallaudet was snug in a cockpit that enclosed all but his head."
"His landing gear was largely enclosed a within bullet shaped fuselage and his three bladed propeller was mounted on the tail. It was this latter feature that we were interested in, of course. We were fortunate in finding that a dear personal friend had actually seen the Gallaudet airplane fly and knew a lot about it. He had even flown in one of the later Gallaudet seaplanes. We were also curious to learn why Gallaudet had been able to make the long shaft to the tail propeller work so nicely, only to have the course of aviation progress move completely away from the concept when it was so obvious that the tail was where the propeller really should be mounted. Certainly, the performance of the Al and A2 proved that."
"As it turned out, the answer was quite simple — he had used a rotary engine, which served as a spinning flywheel that smoothed out the power pulses that can be so destructive to shaft drives. This "torsional resonance" was the problem that plagued the Waco Aristocraft, the Douglas Cloudmaster, the BD-5 and a number of others with shaft driven propellers. Some of the more sophisticated designs like the XB-42, P-39 and P-63 incorporated successful shaft drives, but only at the expense of heavy, costly, high maintenance vibration damper systems and' special operational techniques."
The second mention is at http://affordaplane.com/alumribs.html
"The first airplane to use aluminum tubing for ribs was this one, the Gallaudet A2 Bullet. Built in 1912, the tube ribs were flattened at the ends so rivets could attach them to the caps and spars."

The BD-5 never had a direct shaft drive, the engine was connected to a clutch system by a belt drive with a 1.66:1 reduction


text:
Can a door be shut while in flight?
What is the best way to shut a door that has popped open in flight?
I had a door on a Cessna 172 pop open shortly after takeoff and was unable to get it closed, but I was fortunate enough to be able to quickly circle around and land. I tried reaching across with my right hand, but I was unable to push the door open enough to pull it quickly enough to latch. Is there a way to shut a door?

Source
In this accident of a Cirrus SR22 the pilot became disorientated by an open door and crashed. What procedure should be used for an open door?

Did you try a sideslip?

I can't tell you how many times I was soloing in my flight schools 172 during my training and the pilots door would open on short final. I'm not even phased by them anymore, except when it's -10F then it gets a little cold.

I dk but I should warn you that in Canada it is illegal to enter an airplane while it is in flight.  So.... no hitch-hikers.

Canadians are no fun!

If lower airspeed and the push/pull technique don't get the door closed, I have always had great success opening a window and trying again, especially in Cessnas (check your POH and observe max window open speeds).  This helps equalize the pressure between inside and out and makes the door close much more easily.  The windows are usually very easy to open and close by hand in light planes.
Again, as in the other answers, I emphasize to fly the plane first, and only try to close the door at a safe altitude, during trimmed, safe stable flight conditions.

This is what I was later told would work - especially with Cessna. However I noticed some are saying they slowed the airplane down and that may also increase success. In my case I attempted to re-close at normal cruise speed and could not push against the air stream enough to quickly snap it shut. Thanks for pointing this out.

FWIW, I just put 30 hours on a C182 last week, and the other guy's door came open a number of times. We never slowed, but always opened a window first, and always got the door closed on the first try.  I know anecdotal evidence isn't worth much, but that's my experience.

" I emphasize to fly the plane first" << I don't think this can be emphasized enough. I've read so many accident reports because an air crew became fixated on a problem that wouldn't have resulted in a crash if they had JUST FLOWN THE PLANE.

I've had this happen a few times on aging C152's and in all cases I have been able to simply push it against the airflow enough to pull it closed. On a PA28 with the door the other side of the cabin from the pilot seat, this wouldnt be possible. Not that I have experienced it in a PA28, but I might ask a passenger to attempt the same (hard push followed by a hard pull).
Some things to note:

There's no massive danger of a door slightly ajar, so waiting until  out of a critical phase of flight is advisable (ie, climbed to cruise, clear of any ATZ)
In all but one time I had another competent pilot sitting next to me who can keep an eye out and even hold the controls for a few seconds. Just one reason flying with other pilots is nicer than flying alone.

However, I would suggest that every situation is different. The most important thing is, as always, Aviate first. A light aircraft is unlikely to be critically unable to continue flying with a door ajar. Don't get distracted by something like an ajar door - fly the aircraft.
If in any doubt, land as soon as possible and fix the problem. It would, I think, be acceptable to call "Pan Pan" if you feel you need to expedite a landing.

"There's no massive danger of a door slightly ajar": That is really the most important line - more accidents happen because the pilot is distracted by the door than from the open door itself. Just like in Eastern 401

I once asked my CFI whether we could try it in a training flight in a PA-38, as the doors were a bit  worn and I didn’t want to deal with an open door on one of the early solos without any preparation. He agreed, and we did, and on the push/pull the door handle came off. So ... I‘d recommend to factor in a potentially worse outcome when trying to fix something that’s not really hazardous per se when you establish priorities in a real situation.

Remotely related: here's a training video for flight deck window opening in a 737 during take-off. It stresses that there is nothing mechanically wrong with the airplane and you should continue flying and close it when stable.

I can attest that it may be impossible to close the door of a Mooney in flight, because of the way the airflow gets directed through the hinge section.  At the very least, I (passenger and bombardier) couldn't do it.  This is what we'd suspected going out, though, and we completed the flight as-planned.

Do whatever it says in the POH for your aircraft. This is from the C172S POH, for example:

Accidental opening of a cabin door in flight due to improper closing
  does not constitute a need to land the airplane. The best procedure is
  to set up the airplane in a trimmed condition at approximately 75
  KIAS, momentarily shove the door outward slightly, and forcefully
  close and lock the door.

A C182RG POH says exactly the same thing, but at 80 KIAS instead of 75.

I think OP tried this but couldn't, due to reaching across!

A few points: The trick of pushing the door farther open then slamming it shut doesn't work as well as on a car as the door is generally much lighter weight than a car's, reducing its inertia that helps it slam shut. And the force of the airflow over it prevents it from opening much farther anyway. A sideslip in the direction of the open door can help a lot, though.
But besides the sudden wind noise and potential wind in the cockpit blowing loose items around, it is not an emergency. I've flown (and been flown in) a Cessna 152 when we had removed the passenger door altogether to allow air to air photography. No problem. Just be sure to be buckled in first!

While I was banking a Cessna 152 45 degrees left a few years back, the pilot-side door popped open. That was exciting.
As I recall, closing it took a hard push into the windstream, then a pull as it bounced back. Otherwise, it was just re-closing a car door. The instructor didn't even have me level out first.


text:
Why is the stall speed of an aircraft a specific speed?
I've read in many places that the stall speed is xxx knots for a specific plane.
Is the stall speed of any aircraft fixed or does it change depending on other conditions such as weight, density of air, temperature, humidity, etc.?
Could an aircraft stall at a higher flight speed, depending on the angle of attack?
Secondly, shouldn't lift reduce as speed reduces? So why does the aircraft lose complete lift only at a specific speed?

There are sooo many duplicates of this question.  Please do a search...

Did you do previous research on this? I spent 8 seconds on a google search and came up with these: article from Aircraft Owners and Pilots Association Non Profit, article from Bar-or Aviation, article from Experimental Aircraft Info, ...

... CFI notebook: Stall Performance, Online ground school explanation of stalling, ...etc. and many, many more. Please always do research on every question you post, and if you did do research please explain what sites you have visited and why they aren't helpful, if possible. All of those sites I mentioned above seems to answer your question, and the only thing I did was type "stall speed factors" in the Google search bar.

As a fun fact, even wikipedia have an article on aerodynamic stalling that also seems to answer your question pretty well. See Stall (fluid dynamics).

If this is such an obvious duplicate, why does nobody close it?

@mkrieger1 its not a dupe unless there's a preexisting SE question/answers.  These links are all to other sites, so its a lack of research not a duplicate, unless you can suggest an existing question?  The "related" list are all related but none mention "specific speed" or similar wording.

The stall speed of an aircraft is not fixed; it changes depending on several factors:

Weight: More weight means more lift required to maintain flight, which increases the stall speed. A lighter aircraft will have a lower stall speed.
Air Density: Air density decreases with altitude, which means the stall speed in terms of "indicated airspeed" (IAS) remains the same, but the "true airspeed" (TAS) at which the aircraft stalls increases.
Center of Gravity: A more forward center of gravity requires more lift and can increase the stall speed.
Load Factor (Bank Angle): When an aircraft is in a turn, the load factor increases, and so does the stall speed. This is why an aircraft can stall at higher speeds during steep turns.
Flaps and Wing Configuration: Lowering flaps increases the wing area and changes the wing's camber, allowing the aircraft to stall at a lower speed.
Air Temperature and Humidity: These factors affect air density, which in turn affects the stall speed.
Icing on the Wing: Ice formation on the wings can disturb the smooth airflow and reduce the wing's lift capability. This increases the stall speed because the aircraft must fly at a higher speed to produce the same amount of lift as it would without ice. Ice can also increase drag and affect controllability, making stalls more sudden and harder to recover from.

Also,

Why does the aircraft lose complete lift only at a specific speed?

The aircraft does not lose all lift at a specific speed; instead, it loses lift when the angle of attack exceeds the critical value. The stall occurs due to exceeding the critical angle of attack, not merely a reduction in speed. The "stall speed" is the speed at which, under a specific set of conditions, the wing reaches that critical angle of attack. This speed is variable based on weight, configuration, and other factors.
For example, here's the chart for the stall speed of a Cessna 172 by bank angle. It's only one factor, but it shows how the stall speed is changing with bank angle and flap configuration.

(Source)
As the bank angle increases, the load factor does too. This makes the stall speed increase. With flaps this increase in stall speed is reduced slightly, but that also increases drag so more power will be required.

KIAS = Knots Indicated Airspeed
KCAS = Knots Calibrated Airspeed

Articles I'd recommend for you to read on this topic -

https://skybrary.aero/articles/true-airspeed
https://skybrary.aero/articles/indicated-airspeed-ias
https://skybrary.aero/articles/stall

And ice on wings.

Super great answer to a question lacking research. I'd say you explained everything superbly, it's very informative. By the way, I agree with @GiacomoCatenazzi, ice on the wings are perhaps the most common reason for stalling.

@AircraftEnthusiast007, I didn't think of searching for duplicates before answering... my bad.

Stall is the configuration of airstream around aerodynamic shape that cause detachment of the airstream from the shape surface. The airflow abruptly changes from laminar to turbulent. As a consequence, the force ballance changes abruptly (from dominant lift to dominant drag)
You can have (wing) stall, controls stall and engine stall. But all work exactly the same.
For wing it means loss of lift, for engine it means lost of thrust (propeller, fan blade) or engine stop (compressor blade stall). For controls it means no effect of the inputs.
The state of the wing (propeller, blade, contol) is defined by relative air speed, angle of attack, current wing (propeller, blade, wing-control assembly) geometry, air density and incomming airflow (laminar, turbulent or mixed). Those are all the variables affecting the stall conditions.
The condition easiest to control is airspeed, then AoA and wing geometry. Rest is out control.
So for one airplane - one registration number, one flight - you have infinite ammout of stall speeds.
Luckily it is quite well behaving function of two/three variables, considering all other reasonably constant.
That's why you have a table of stall speeds.
Flaps are designed to alter stall properties. Higher flaps mean lower stall speed and allow higher AoA than no-flaps. In expense of higher drag.
Angle of attack affects the stall speed significantly, so the stall speeds are tabelated for given flaps and listed AoA.
If you have ice on wings (propeller, fan, blade,...) such tables are of no use - stall speeds are (much) higher, unpredictably higher. In turbulent air (storm cloud, behind another plane,...) such tables are of no use either - you want to get out of such dirty air as soon as possible and regain control.
Secondary parameters are:

Weight - Heavier plane needs higher AoA to maintain ballance (higher lift demand) and is easier to stall. (Nose down means descending)
Ballance - Aft centre of gravity "pushes" nose up naturally increasing AoA. Must be countered by elevators. (Elevators are closer to their nose-down limit)
Yaw, bank - those alter the net force ballance out of the "sideview plane" reducing the wings' efficiency and ballance. (in other words, increase the stall speed)
Damage, icing - altered geometry means reduced efficiency and increased stall speed
air pressure (altitude) - higher pressure mean higher air density at the same temperature. Higher altitude means lower air density and higher stall speed.


text:
GNS 430 Instrument Panel Self Test Page OBS readout does not agree with OBS Hdg selected on CDI
Our Newly installed Overhauled GNS 430 OBS readout on the Instrument Panel Self Test Page does not agree with the Heading selected on our CDI.  Prior to the 430 overhaul they agreed perfectly. Difference is 5 degrees.  Is this a configuration setup issue on the 430?
Note: There is a configuration page in the installation manual which describes a OBS calibration  "This page allows the user to verify the CDI outputs from the VOR/LOC/GS receiver as well as the OBS resolver input to the VOR receiver" but im hesitant to start poking around in config without confirmation.

There is nothing specific in the Users manual about a what Ill call a "split" indication on the Self Test page other that the OBS selected Heading and the self test readout on the Garmin should match wihtin 2 degrees or so, I think the Garmin readout confirms that the OBS heading input to the VOR receiver is working.   Garmin did the overhaul , getting an answer from them is challenging. But No I haven't checked with them,,,yet. But now that you mentioned it I will call the Avionics shop on Monday, Thanks.


text:
How does aircraft weight affect landing distance?
I am a private pilot. I posed a question to instructors in the flight school and got differing answers. For a given aircraft, landing at the same speed, with everything the same except for landing weight, and using maximum braking without skidding the tires, which will stop in a shorter distance after the wheels touch down:  the plane at max gross weight, or the same plane lightly loaded?
I submit that because the heavy plane has more energy to dissipate, it would take longer to stop. Some instructors said that because there is more weight on the wheels, the heavier plane would stop in a shorter distance. I think it is a simple energy conversion physics issue.

First "because the heavy plane has more energy to dissipate, it would take longer to stop" isn't necessarily true. More energy just means the brake gets hotter after the plane lands and nothing else. What actually makes a difference is aerodynamics, like air brakes, spoilers, reverse thrust. Also you made a very unrealistic requirement that airspeed being equal. Say you have an airshow and want to show off short field landing technique you would always unload the plane to nothing but minimum fuel and the thing just lands like feather.

Pretty sure you are right. That's one of the reasons why aircraft dump fuel before landing in an emergency return to field.

Interesting question, but know that in the "real world" (with larger airplanes, where the differences are more exaggerated than a light airplane) landing distance goes down with a decrease in weight, but this is mainly attributed to the reduction in approach speed as the weight decreases.  It may also be why you are getting different answers: some people may be missing the significance of the "at the same speed" point and answering just based on knowledge of actual airplane performance charts.

@user3528438: A heavier airplane will decelerate more slowly than a light one (because A=F/M, and increasing M decreases A), thus taking longer to stop, thus having a longer landing roll.

If you discount aerodynamic effects, and assume the same landing speed, on a theoretical level mass makes no difference. The additional kinetic energy to be dissipated is exactly cancelled by the additional normal force. The kinetic energy is given by the formula:
E = 1/2 mv², where

E is the kinetic energy
m is the vehicle's mass
v is the speed at the start of braking

The work done by braking is given by:
W = μmgd, where

W is work done
μ is the coefficient of friction between the road surface and the tires
g is the gravity of Earth
d is the distance travelled

The braking distance given an initial speed v is then found by putting W = E, from which it follows that
d = v²/2μg

d = minimum stopping distance
v = velocity when brakes were applied
μ = coeff. of friction between wheels and road
g = gravitational constant

Mass is removed from the equation. The kinetic energy is tranferred into heat, so the larger the mass the more heat is generated. But theoretically the stopping distance is unaffected.
In reality, though, the coefficient of friction of tires does not remain constant with changing normal force. As normal force increases the coefficient of friction (μ) of tires decreases.
Since the μ does not remain linear with mass a heavier plane will have an increase in kinetic energy which is higher than the corresponding increase in friction of the tires, thus a longer stopping distance.
All of this assumes that “maximum braking” means you have as much brake power available as the maximum friction force of the tires. Above a certain weight/speed this will not be the case for an airliner. They are designed for a particular amount of deceleration force at MTOW and that will be less than the amount of friction tires can provide on a dry runway. (See this question for more details on that.) That will also cause a heavier plane to roll farther.

Note that usually on dry surface the brakes exert much less force than the tires could handle.

@JanHudec Thanks. Added a paragraph about that

Yes the maximum friction (and therefore braking) force is a linear function of weight. The higher braking force cancels out the higher kinetic energy, if we assume:

That the landing speed is equal at the higher weight.
That the lift dumpers are not operated.
That all the wheels have brakes.
That the brakes can get rid of all of the heat at the higher weight, without blowing the tyres.

Landing Speed.
Braking distance is a quadratic function of touchdown speed. For a small weight increase, we can maintain the same landing speed without much safety implication. Sure airliners dump fuel when attempting a landing close to max gross weight, but that is mainly to limit the touchdown slam, the main gears are not dimensioned for doing this at TO weight. Making the observation at the same landing speed is a really important limitation though, since braking distance is equal to landing speed square.
Residual lift. Lift dumpers remove lift: just after touchdown, the wing still creates considerable lift which reduces the normal (and therefore braking) force. Since the landing speed does not change in our assumptions, the lift decrease is the same, regardless of weight: $ F_N = W - L + \Delta L$. If we take two gross weights and work out the percentage of down force, we get:

So the higher landing weight keeps a higher downforce percentage after deploying spoilers etc. If we consider residual lift, the higher weight causes a shorter braking distance.
Nose Wheel Brake.

Usually, only the main wheels have brakes, but braking creates a forward moment which reduces the downforce on the main wheels. The magnitude of the effect depends on the height of the c.g. off of the ground, but if the nose wheel has no brakes, this effect increases braking distance at higher weight.
Heat buildup
This is another factor that increases quadratically with landing velocity, and only linearly with weight. The brakes are dimensioned for emergency stop below V1 after engine fail, so they will cope with a normal landing at normal weights.
All in all, there is one effect that decreases landing distance as function of landing weight, and one that increases landing distance. We could say that they cancel each other out and that at the same landing speed and within normal limits, braking distance is independent of weight.
But the very shortest landing distance is at the very lightest weight: stay just above stall speed for the weight, even a small reduction is speed has a large effect on distance.

As a practical matter, the aircraft you describe will not fly as you assume. You would have to land very differently at the lighter weight to get the plane on the ground at the same speed as at the heavier weight. With normal landing technique you will touch down a good bit slower at the lighter weight. This will result in a much shorter rollout, as kinetic energy varies with speed squared.
The other answers deal better with your theoretical impossibility.)

The key to this question is "maximum braking without skidding the tires".
With a clean dry surface, the lighter plane at equal speed stops faster.  On a slippery or icy surface, the tables are turned, and a lighter plane will skid much more easily and take longer to stop, due to less traction.  The brakes stop the wheels, but the wheels will not stop the plane.
Notice ABS brakes will not help here, as they release the wheel as soon as it starts to skid.
Under slippery conditions, it is good to dump as much lift as you can once the plane is down. This would include raising flaps and using spoilers to maximum.  And reverse thrust is certainly a good thing to have too.
Experience in the type of plane you fly will help fine tune this knowledge, and a slower landing speed a lighter plane can manage has major impacts on landing roll-out distance, but beware the slippery surface when light.  Here stopping distance is much more unpredictable, and doubling the normal expected stopping distance is not a bad idea.

One thing is right in your demonstration: braking distance is independent of airplane mass. However, it is the braking force that stop the airplane, not the heat produced by braking. The heat and noise produced during braking only consume a small portion of the kinetic energy of the airplane.
The practice of wheel braking has been in use for over 1,000 years. But as far as literature review can go, It looks like the theory of wheel braking has not been correctly understood by the academics and the industry.

Welcome to aviation.SE! As a Q&A site, we expect answers to answer the specific question that was asked. We also like to see sources and references where possible. The [tour] might be interesting if you're new here.

" The heat and noise produced during braking only consume a small portion of the kinetic energy of the airplane" This begs the question of where do you think this energy goes, if not into the brake discs?